The present disclosure relates to an orientation film material and is applicable to a liquid crystal display device having a photo-orientation film for example.
Display in a liquid crystal display device is carried out by applying an electric field to liquid crystal molecules in a liquid crystal layer interposed between a pair of substrates, thereby changing the orientation directions of the liquid crystal molecules, and thus changing the optical characteristic of the liquid crystal layer. In a liquid crystal display device, an orientation control film having a liquid crystal orientation control capability is formed at each of the interfaces between a liquid crystal layer and a pair of substrates holding the liquid crystal layer in between. The orientation control film comprises an organic film such as a polyimide film or the like and is also described as an orientation film.
Japanese Published Unexamined Application No. 2011-170031 (Patent Literature 1) or U.S. Pat. No. 8,648,988 (Patent Literature 2) corresponding to it discloses that an orientation film has a two-layered structure comprising a photo-orientation film and a high film-strength orientation film. It is disclosed that the photo-orientation film is formed by using a polyamide acid ester containing the polyamide acid ester having a cyclobutane by not less than 80% as a precursor and the high film-strength orientation film is formed by using a polyamide acid as a precursor.